With robots, preferably delta robots with three or more axes, servomotors and downstream mechanics, for example the main arms and their bearings, are usually arranged symmetrically in order not to render kinematic transformation unnecessarily complicated. Such delta robots are known, for example, from EP 0 200 369 A1 or EP 1 293 691 B1.
After assembly and the connection of the servomotors to a master controlling means have been completed, the positions of the drives to the associated measuring systems, preferably absolute rotary transducers located on the axles of the servomotor, must be calibrated. The coordinates or dimensions and positions of the servomotors, main arms, forearm bars and joints can be entered into the controlling means and stored. To bring the drives into a position known to the kinematic transformation, the main arms are brought into the position in which the joints at the outer end of the main arms lie in the same horizontal plane as the axles of the servomotors. Since these positions are located in a free three-dimensional space for the fitter, setting aids, which are mounted to the support structure at which the servomotors are attached, are used to function as stop for the main arms.
These setting aids themselves must, just as the support structure for the servomotors, be manufactured very precisely, so that the assembly area for the setting aid to the position of a servomotor and thus to the servomotor axle is subjected to only small tolerances, if possible, as inaccuracies and tolerances in these areas can add and lead to variations with respect to the theoretically assumed parameters or measures stored in the controlling means.
These variations lead to variations in the position of the positioning plate where products are picked up and placed, and also to inaccuracies in the positioning of products. Moreover, mechanical loads can occur at the joints if the movements do not take place as theoretically calculated in the kinematic transformation.
As an alternative, setting aids can also have mounting (reference) surfaces at a support frame to which the support structure for the servomotors is attached, the surfaces being provided for the setting aid or aids. Here, the influence of processing accuracies and tolerances is not less critical.
All these known procedures have in common that calibration via such setting aids is not very precise, and above all, there is a disadvantage in that the setting aids are usually not delivered together with the robot but have to be taken along from the works by the service engineer, if, for example, a servomotor has to be replaced and subsequently calibrated on site.